Superconducting materials have zero resistance. As such, they can be used in many applications. These range from strong magnets in medical magnet resonance imaging to power transmission.
So far, all known superconductors require cooling to turn them into this state of zero resistance. Researchers at the University of Bristol are working to unravel the mechanism of superconductivity in a variety of materials. Completing our understanding will help to find new record superconductors. It will also help novel applications.
High-pressure Superconductivity
A team lead by Dr Sven Friedemann studies superconductors at high pressures. This includes recently found hydrogen-compounds like sulphur hydride. This compound possesses a superconducting temperature of -70 °C.
Researchers use diamond anvil cells to generate pressures up to 2 million atmospheres. This is necessary to form these compounds and necessary to make them superconduct.
The team studies the electronic and magnetic properties of high-pressure superconductors. This research is supported by the European Research Council and the EPSRC.
Resistance measurement showing superconductivity in hydrogen sulphide.
Unconventional Superconductivity
Researchers from the University of Bristol study the mechanism of Superconductivity in Cuprate Superconductors. This research is supported by both the UK research council EPSRC and the European Research Council. The research focuses on the electronic and magnetic ground state and excitations.
Recent results show that high temperature superconductivity in layered cuprates can develop from an electronically ordered state. This is called a charge density wave.
Checkerboard pattern due to the modulation of the atomic positions in the CuO2 layers of YBa2Cu3O6+x caused by the charge density wave
Probing the superconducting gap
We use multiple probes to investigate the structure of the superconducting energy gap. As the energy gap is closely linked to the pairing interaction, our measurements give important insight about how electron pairing occurs.
We combine very low temperatures (~60mK) with radio-frequency technique. This makes high resolution measurements of the magnetic response of the superconducting phase. From the temperature and field dependence of the magnetic response we can infer the structure of the superconducting gap.
Recently, we demonstrated for the first time how the non-linear Meisner effect can provide detailed information about the underlying gap structure.
Gap structure found in one of the iron-based superconductors studied
